/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.result.condition;

import org.springframework.http.server.PathContainer;
import org.springframework.lang.Nullable;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.util.pattern.PathPattern;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;

/**
 * A logical disjunction (' || ') request condition that matches a request
 * against a set of URL path patterns.
 *
 * @author Rossen Stoyanchev
 * @author Brian Clozel
 * @since 5.0
 */
public final class PatternsRequestCondition extends AbstractRequestCondition<PatternsRequestCondition> {

    private final SortedSet<PathPattern> patterns;


    /**
     * Creates a new instance with the given URL patterns.
     *
     * @param patterns 0 or more URL patterns; if 0 the condition will match to every request.
     */
    public PatternsRequestCondition(PathPattern... patterns) {
        this(Arrays.asList(patterns));
    }

    /**
     * Creates a new instance with the given URL patterns.
     */
    public PatternsRequestCondition(List<PathPattern> patterns) {
        this(new TreeSet<>(patterns));
    }


    private PatternsRequestCondition(SortedSet<PathPattern> patterns) {
        this.patterns = patterns;
    }

    public Set<PathPattern> getPatterns() {
        return this.patterns;
    }

    @Override
    protected Collection<PathPattern> getContent() {
        return this.patterns;
    }

    @Override
    protected String getToStringInfix() {
        return " || ";
    }

    /**
     * Returns a new instance with URL patterns from the current instance ("this") and
     * the "other" instance as follows:
     * <ul>
     * <li>If there are patterns in both instances, combine the patterns in "this" with
     * the patterns in "other" using {@link PathPattern#combine(PathPattern)}.
     * <li>If only one instance has patterns, use them.
     * <li>If neither instance has patterns, use an empty String (i.e. "").
     * </ul>
     */
    @Override
    public PatternsRequestCondition combine(PatternsRequestCondition other) {
        List<PathPattern> combined = new ArrayList<>();
        if (!this.patterns.isEmpty() && !other.patterns.isEmpty()) {
            for (PathPattern pattern1 : this.patterns) {
                for (PathPattern pattern2 : other.patterns) {
                    combined.add(pattern1.combine(pattern2));
                }
            }
        } else if (!this.patterns.isEmpty()) {
            combined.addAll(this.patterns);
        } else if (!other.patterns.isEmpty()) {
            combined.addAll(other.patterns);
        }
        return new PatternsRequestCondition(combined);
    }

    /**
     * Checks if any of the patterns match the given request and returns an instance
     * that is guaranteed to contain matching patterns, sorted.
     *
     * @param exchange the current exchange
     * @return the same instance if the condition contains no patterns;
     * or a new condition with sorted matching patterns;
     * or {@code null} if no patterns match.
     */
    @Override
    @Nullable
    public PatternsRequestCondition getMatchingCondition(ServerWebExchange exchange) {
        if (this.patterns.isEmpty()) {
            return this;
        }
        SortedSet<PathPattern> matches = getMatchingPatterns(exchange);
        return (!matches.isEmpty() ? new PatternsRequestCondition(matches) : null);
    }

    /**
     * Find the patterns matching the given lookup path. Invoking this method should
     * yield results equivalent to those of calling
     * {@link #getMatchingCondition(ServerWebExchange)}.
     * This method is provided as an alternative to be used if no request is available
     * (e.g. introspection, tooling, etc).
     *
     * @param exchange the current exchange
     * @return a sorted set of matching patterns sorted with the closest match first
     */
    private SortedSet<PathPattern> getMatchingPatterns(ServerWebExchange exchange) {
        PathContainer lookupPath = exchange.getRequest().getPath().pathWithinApplication();
        TreeSet<PathPattern> pathPatterns = new TreeSet<>();
        for (PathPattern pattern : this.patterns) {
            if (pattern.matches(lookupPath)) {
                pathPatterns.add(pattern);
            }
        }
        return pathPatterns;
    }

    /**
     * Compare the two conditions based on the URL patterns they contain.
     * Patterns are compared one at a time, from top to bottom. If all compared
     * patterns match equally, but one instance has more patterns, it is
     * considered a closer match.
     * <p>It is assumed that both instances have been obtained via
     * {@link #getMatchingCondition(ServerWebExchange)} to ensure they
     * contain only patterns that match the request and are sorted with
     * the best matches on top.
     */
    @Override
    public int compareTo(PatternsRequestCondition other, ServerWebExchange exchange) {
        Iterator<PathPattern> iterator = this.patterns.iterator();
        Iterator<PathPattern> iteratorOther = other.getPatterns().iterator();
        while (iterator.hasNext() && iteratorOther.hasNext()) {
            int result = PathPattern.SPECIFICITY_COMPARATOR.compare(iterator.next(), iteratorOther.next());
            if (result != 0) {
                return result;
            }
        }
        if (iterator.hasNext()) {
            return -1;
        } else if (iteratorOther.hasNext()) {
            return 1;
        } else {
            return 0;
        }
    }

}
